The voltage of an electromagnetic wave propagating in a coaxial cable with uniform characteristic impedance is $V(l)= e^{-\gamma l +j\omega t }$ Volts, where $l$ is the distance along the length of the cable in meters, $\gamma=(0.1+j40)m^{-1}$ is the complex propagation constant, and $\omega=2 \pi \times 10^{9}$ rad/s is the angular frequency. The absolute value of the attenuation in the cable in dB/meter is__________.